1. Field of the Invention
The present invention relates to a fluorene compound for an organic light-emitting element and an organic light-emitting element using the fluorene compound.
2. Description of the Related Art
In the organic light-emitting element, a thin film containing a fluorescent organic compound or a phosphorescent organic compound is held between an anode and a cathode, and electrons and holes are injected from the respective electrodes. Consequently, excitons of the fluorescent organic compound or the phosphorescent organic compound are generated, and the light emitted when the exciton returns to a ground state is used in the element.
Recently, the organic light-emitting elements have developed significantly. Since desired features now include light-emitting devices having a high luminance at a low applied voltage, a diversity of wavelengths of emitted light, high-speed performance, low profile, and light weight, the possibilities of wide-ranging applications have been explored.
However, these possibilities require an output of light having a higher luminance or a higher conversion efficiency. Furthermore, emission of blue, green, and red light with higher color purity is required for full color displays or the like. These issues have not yet been solved satisfactorily.
Much research has been conducted on aromatic compounds and fused polycyclic aromatic compounds serving as luminescent organic compounds for light-emitting layers or the like. However, one cannot say that a fully satisfactory compound has been obtained from the viewpoint of the luminance of emitted light and the like.
Documents related to the present invention include Japanese Unexamined Patent Application Publication Nos. 11-144875, 11-162642, 2004-43349, 2004-277368, and 2004-277377 as patent documents and Macromolecules, 36, 8986 (2003) and J. Org. Chem., 70, 3009 (2005) as non-patent documents. However, no disclosure has been made with respect to a fluorene compound, as disclosed in the present invention, serving as a material for an organic light-emitting element and having a high triplet excited state T1 level based on the presence of a steric hindrance group on a fluorene ring. There is no example in which such a sterically hindered fluorene compound is applied to an organic light-emitting element.